A few times I have been asked to give a talk to students and rather than just perform magic for them, I took one trick and — without offering any explanation — ask them how they would go about trying to figure out how it was done. It wasn't about the answers, it was about asking the right questions.

Gradually, they realized they would want to have different students watching from different places, that would want to videotape it to watch it multiple times, possibly in slow motion, and most importantly, to have me perform it again under a variety of different conditions. (Can we shuffle the cards? Can we choose a different one? Can we bring the deck of cards?)

Essentially the students re-invented the scientific method on the spot.

Along the way, they had offered up suggestions as to how the trick might have been accomplished. After all, in science you need a hypothesis to test. One of them was most of the way to being right, although I never told her at the time.

Recently Michael Shermer, writing for Scientific American, recently took the same approach to a more everyday topic: the resurrection of Jesus. How do you evaluate the truth of claims you can't investigate for yourself? If you're a skeptic, how can you know anything is true.

Michael Shermer

By way of introduction:

There are many propositions for which we have adequate grounds for certainty as to their truth:There are 84 pages in this issue of Scientific American. True by observation.

Dinosaurs went extinct around 65 million years ago. True by verification and replication of radiometric dating techniques for volcanic eruptions above and below dinosaur fossils.

The universe began with a big bang. True by a convergence of evidence from a wide range of phenomena, such as the cosmic microwave background, the abundance of light elements (such as hydrogen and helium), the distribution of galaxies, the large-scale structure of the cosmos, the redshift of most galaxies and the expansion of space.

These propositions are “true” in the sense that the evidence is so substantial that it would be unreasonable to withhold one’s provisional assent. It is not impossible that the dinosaurs died a few thousand years ago (with the universe itself having been created 10,000 years ago), as Young Earth creationists believe, but it is so unlikely we need not waste our time considering it.

Then there are negative truths, such as the null hypothesis in science, which asserts that particular associations do not exist unless proved otherwise. For example, it is telling that among the tens of thousands of government e-mails, documents and files leaked in recent years, there is not one indication of a UFO cover-up or faked moon landing or allegation that 9/11 was an inside job by the Bush administration. Here the absence of evidence is evidence of absence.

Other propositions are true by internal validation only: dark chocolate is better than milk chocolate; Led Zeppelin’s “Stairway to Heaven” is the greatest rock song; the meaning of life hinges on the number 42. These types of truth are purely personal and thus unverifiable by others. In science, we need external validation.

When I was speaking to the students, I eventually moved on to the more difficult question:

If this were accomplished by magic (instead of some sort of trick), how would you know?

Most people don't know that it's impossible. You can't use a lack of an explanation to justify an explanation. The "I don't know, therefore magic" argument is invalid. Shermer's full piece does a fantastic job of explaining why.